The present invention relates to an interphase insulating sheet for a rotating electric machine, a rotating electric machine, and an electric compressor for a vehicle.
The wave winding, which is a type of the distributed winding, is known as a method for winding a coil on a stator core of a rotating electric machine. For example, in a three-phase alternating (AC) current rotating electric machine, coils of three phases, that is, a U-phase coil, a V-phase coil, and a W-phase coil, are inserted in a plurality of slots formed in a stator core of the rotating electric machine by wave winding. Each of the coils has coil ends that extend out from the opposite axial ends of the stator core (i.e. the end of the lead wire side and the end on the side opposite to the lead wire side). For insulation of the coils from each other, an interphase insulating sheet is interposed between the coil ends of any two different phases.
A typical interphase insulating sheet has a pair of annular portions, one extending out from the lead wire side of the stator core and the other annular portion extending out from the side opposite to the lead wire side, and a plurality of bridge portions that connects the paired annular portions to each other to thereby form the interphase insulating sheet of a cylindrical shape. The interphase insulating sheet is mounted to the stator core by inserting the U-phase coil in each of the slots for the U-phase and then inserting the bridge portions in each of the slots for the V-phase. The interphase insulating sheet that is formed in a cylindrical shape is resilient to deformation, and coil ends of the U-phase coil extend out from the stator core. Therefore, due to its elasticity, the shape of the interphase insulating sheet may be disordered and the interphase insulating sheet may extend inwardly from the slots toward the center of the stator core, thus hindering the mounting of the V-phase coil or the W-phase coil to the stator core. Such disordering in shape of the interphase insulating sheet may occur more frequently with an increase of the number of the polarities of the rotating electric machine.
For example, Japanese Unexamined Utility Model Application Publication No. 62-168760 discloses an interphase insulating sheet for insulating coil ends of different phases. The interphase insulating sheet includes two strip-shaped insulating portions each having a linear slit. The slits formed in the interphase insulating sheet may be enlarged and the parts of the interphase insulating sheet across the slits may be moved so as to overlap with each other, forming wrinkles in the sheet. This makes it possible for the interphase insulating sheet to be put into close contact with the curved surface of the coil ends.
The interphase insulating sheet for insulating coil ends of different phases disclosed in the above publication has the silts at positions that correspond to the positions of the coil ends of the U-phase coil which is first mounted to the stator core. Although the above enlargement of the slits or the overlapping in the interphase insulating sheet enables close contact between the interphase insulating sheet and the coil end of the U-phase coil, a clearance or no-insulating portion may be created, and which may result in an impaired insulating function between the coil ends of the U-phase coil and the coil ends of the V-phase coil.
Mounting the V-phase coil to the stator core applies a large load in tensioning direction or compressing direction to the interphase insulating sheet. There is a fear that application of such load decreases the strength of the strip-shaped insulating portions at the slits and the insulating portions are torn at the slits. Such damaged insulating sheet may cause further impairment of the insulating function of the interphase insulating sheet.
The present invention is directed to providing an interphase insulating sheet for a rotating electric machine that prevents the shape of the interphase insulating sheet from being disordered without impairing the insulating function and the strength of the interphase insulating sheet.